No idea if that is common or not. I have only converted the one. But yes, you do need a threaded spacer. Wacker engines could fix you up. I purchased one from him the other day (As my machinist buddy is in florida, darn those retired guys) because I was in to much of a hurry to wait for a free one. lol. He seems like a great guy, give him a call and I am sure he can tell you exactly what you need.